Starting with the release of 2017 data (in September 2018), American Community Survey began providing health insurance data in age categories that are reflective of the current health insurance climate under the Affordable Care Act. With the implementation of the ACA, the definition of a qualifying child changed to those under age 19 at the close of the calendar year. Previous health insurance data tracking was done with children defined as ages 0-17 and adults defined as 18+. With the ACA's new definitions, health insurance data for children is now defined as 0-18 and adults as 19+.
New indicators were created to account for these changes for Adults with Health Insurance and Children with Health Insurance. Data starting with the 2017 time period is now stored under these new indicators. The old indicators are now designated with the age groups they represent in the indicator titles (Adults with Health Insurance: 18-64 and Children with Health Insurance: 0-17) and have been designated as "archived" indicators. These old versions of the indicators, with data up to the 2016 time period are still being displayed, but will not be updated further so long as ACS continues to use the new ACA definitions of adults and children.
To read more about this change, please see American Community Survey's methodology and documentation here: